I recently bought a bulk quantity of 5w/30 fully synthetic oil, aimed at Ford Zetecs which is ACEA rated A1/B1/A5/B5.
I was hoping to also use this in the newer Vauxhalls as well, but according to their recent manuals it states that only oils of grade A3 5w/30 should be used for all types of their engines and A1/A5 oils are "expressly forbidden as they can cause long term engine damage under certain conditions."
It seems that the A1/A5 oil has a slightly lower viscosity and is aimed at fuel efficiency but can't find a definitive answer as to why it could be damaging. The ACEA does state that this grade is not suitable for some engines, but no explanation.
Any suggestions would be appreciated, as my local motor factor wants almost double the amount for the A3 rated oil.

A1/A5 Requires a HTHS viscosity between 2.9 and 3.5cP at 150C and A3 requires it to be at least 3.5cP at 150C. HTHS is an acronym for High Temperature High Shear and it tests exactly what it implies; oil viscosity under high temperature and high stress.

most euopean manuals would give that requirement.

shell helix ultimate and castrol edge down here are 5w-30 but A3. you've got me wanting to use one of those... except i have 3 years worth of ILSAC engine oil,.,

Thanks...
So having a low HTHS rating, the A1/A5 oil could cause oil pressure to drop and accelerated wear on an engine not designed for it... presumably on a low performance petrol this would be less critical but best to stick to the A3 as recommended.

IIRC, but don't remember where I read it, you could use A3 where A1 is called for, but not the other way around.

Memory is a bit fuzzy on that.

I have a ACEA Y2008 question.

Refer: http://www.acea.be/images/uploads/files/20090105_081211_ACEA_Oil_Sequences_Final.pdf

How come under requirement 2.7 Wear and 2.8 DI diesel piston ring cleanliness & ring sticking, ACEA A5/B5 is more stringent than ACEA A3/B3?
Does that imply that A3/B3 although thicker it does not protect and clean as well as A5/B5?
Or perhaps A3/B3 is thicker and it should protect better, hence the requirement is not as stringent as A5/B5?

A5/B5 is the "low viscosity" version of A3/B4, which is more stringent/higher performance than A3/B3.

Charlie

TwsT, ACEA Ax(gasoline) and Bx(diesel) were introduced as separate categories in 1996,later in 2004 the gasoline and diesel categories were combined. ACEA has raised the bar of performance for oils applying for certification but the category designation has remained the same (examine the links below). Regarding the A3/B3 category, all kinds of oil can qualify-from Gr.I to synthetics… on the other hand, the vast majority of A5/B5 (and A1/B1) oils are Gr.III and up. Passenger car Gr.I mineral oils having A3/B4(gasoline and direct-injection diesel) level of approval are rarity-it`s the mixed-fleet HDEO's that usually carry it. To guarantee a minimum DI-performance for A3/B3 oils, ACEA has mandated that they should also pass the VW DI diesel test (but the criteria here are not so demanding).Up to 2007,the wear test is CEC-L-51-A-98 on Mercedes-Benz om602 prechamber turbocharged engine-with limits identical for all Ax/Bx categories! In 2008,ACEA introduces the CEC L–099-08 ,on MB 646 DI common-rail diesel with higher demands for A3/B4 and A5/B5 categories. Although these tests are held on MB engines, this manufacturer still prohibits the use of oils with HT/HS<3.5 cP in their equipment !!!
Manufacturers’ specifications are stringer and demand a certain ACEA level from the applicant oils.

http://www.ueil.org/automotive/documents/ACEA2008Sequences.pdf

ACEA Sequences by revision:

2002:
http://www.utc.fr/~tthomass/Themes/Unites/unites/infos/huile/Publication_Oil_Sequences.pdf

2004:
http://www.acea.be/images/uploads/pub/ACEA2004_rev%20Sep05.pdf

2007:
http://www.acea.be/images/uploads/pub/070308_ACEA_sequences_2007_LD_and_HD.pdf

2008:
http://www.acea.be/images/uploads/files/20090105_081211_ACEA_Oil_Sequences_Final.pdf

Hi Rollins,

Appreciate your explanation to my query. To summarise what I had learn today; A3/B3 ranges from group 1 to group 5 base oil, hence the requirement are not as stringent as A5/B5 which are mostly group 3.

But can I assume if A3/B3 are better(higher) group oil, then it should perform better than A5/B5 in the wear test? After all, the ACEA for A3/B3 is only minimium standard which it should meet, in reality it could perform much better?

Actually, it’s the manufacturers(engine design evolution… or forced by legislation) that necessitate a change of an existent category ..or the introduction of a new one. More or less, the market(or the OEM demand) channels things- for example nowadays no modern diesel Euro engine leaves factory with –or specifies- A3/B3 service oil(regardless of base) -it would be A3/B4 …or A1/B1..or A5/B5 –all these now usually combined with a “C”-aftertreatment compatible- category ! And ACEA as an association governed by the Euro companies reflects the manufacturers’ demands-and their “oil sequences” is a very informative and orderly system.

-it`s the fact that A3/B3 have limited applicability to nowadays diesel engines-their use would contradict the OEM recommendation..

Look what ford says about their specified oils:
http://www.atiel.org/members/pdf_files/ACEA%20Stow.pdf

Opel/GM (Quote:"Industry oil standards like ACEA, API are result of
compromises
• Requirements are not fully tailorable to individual
OEM needs like..etc")
http://www.strasseschweiz.ch/dcs/users/2/Buetehorn.pdf
..etc.
Manufacturers’ specs are stricter(and perhaps broader) and should be sought first on the bottle-I `d prefer a A3/B3 and OEM certified oil(with the respective category) to any higher-ranked ACEA oil void of it…well,most of the time(there are some not-so-demanding applications).

In ACEA test "reality",or in real "service" reality?Well,no one knows for sure.And A1/B1 or A5/B5 are not suitable for many engines.The manufacturer knows best.That's why the presence of a relevant OEM approval is (almost) a must.

fwiw redline 5w20 says on bottle acea A5/B5 and their 5w30 oil says A3/B4 any comments?

The A5/B5 has a HTHS spec of 2.9-3.5; A3/B4 >3.5
5W20 is lighter than 5W30, therefore the viscosity difference.
Other specs are the same between the 2 ACEA ratings, therefore additive systems may be very similar.

Charlie

Sorry for my late. I was reading this topic found by google.
Answering your question


It could damage because the Drain Interval. A A1 oil is suitable for your engine since the drain intervals are reduced. If you read the GM report posted on this topic, you will see that for the same model that can't use a GM-LL-A-025 oil a SM/ILSAC GF4 (US spec) oil is recommended instead but the change interval is reduced by a quarter of EU spec.